The present invention refers to a reciprocating compressor with two pistons driven by a linear motor, to be applied to refrigeration systems.
In the reciprocating compressors with two pistons driven by a linear motor there is a reduction in the number of parts with relative movement, as compared to the conventional constructions of compressors with a rotary motor, which results in gains in terms of dissipated power in the bearings.
In a known construction of a reciprocating compressor driven by a linear motor, with two pistons being mounted axially aligned to each other and reciprocating inside the same cylinder, the gas suction and compression operations result from opposite axial movements of both pistons inside the cylinder, respectively by mutual movements of separation and approximation, said pistons being individually coupled to respective actuating means, usually tubular and external to the cylinder and provided with magnets, which are axially impelled upon energization of respective linear motor portions usually affixed outside the cylinder.
The gas suction occurs through the pistons themselves and is controlled by suction valves, each positioned on the top of the respective piston.
In one of the known solutions, the gas discharge is effected through a radial slot produced in the lateral wall of the cylinder in a median region thereof, which is defined when the pistons are in a maximum approximation condition (upper dead point), said radial slot being opened towards said median region through a median radial discharge orifice, the gas discharge being controlled by a discharge valve positioned in said slot and conducted to an opening condition during the mutual approximation movement of said pistons.
In order to minimize the losses during compression, the pistons should reach a maximum mutual approximation, practically closing the median radial discharge orifice of the cylinder. A disadvantage of this solution is that, since the discharge orifice is located laterally in the cylinder, when the pistons reach the maximum mutual approximation (upper dead point), they cover almost totally the discharge orifice, impairing the discharge of the gas.
In this case, it should be foreseen a dead volume (FIG. 1) produced in the cylinder body, close to the discharge orifice, in order to store gas at the end of compression. However, this solution reduces the volumetric yield of the compressor.
Another option is to determine a movement for the pistons which, when in the maximum mutual approximation, does not determine the closing of the orifice. In this case, however, it occurs the formation of a volume between the pistons at the region of the discharge orifice, resulting in constant yield loss (FIG. 1).
Besides these deficiencies, another disadvantage of the constructions known in the art refers to the fact that the discharge orifice is located laterally in the cylinder, impairing the exit of the gas present in the region which is diametrically opposite to that where the orifice is provided in the cylinder, at the end of compression. These effects, whether combined or isolated, reduce the volumetric yield of the compressor.
Thus, it is an object of the present invention to provide a reciprocating compressor with a linear motor, having minimum vibration during operation and maximum volumetric yield, suppressing the lateral gas discharge and the volume of the gas discharge therein.
This and other objectives are achieved by a reciprocating compressor with a linear motor, comprising a cylinder; a pair of pistons provided inside the cylinder and axially aligned to each other; a linear motor driving the pistons in opposite directions; a suction valve provided in at least one of the pistons, controlling the gas admission to the inside of the cylinder; and a discharge valve provided in order to control the discharge of the gas admitted inside the cylinder, at least one of the pistons being provided, on its top face, with a respective discharge valve, in order to control the axial discharge of the gas through said piston.